Method of and means for reproducing and transmitting pictures



March 8, 1932.

R. H. RANGER METHOD OF AND MEANS FOR REPRODUCING AND TRANSMITTINGPICTURES Original Filed Feb. 26, 1924 Sheets-Sheet l anvemtoz RKHARDHUWLAND RANGER 3391 is Qua/"W March 8, 1932. R RANGER 1,848,840

METHOD OF AND MEANS FOR REPRODUCING AND TRANSMITTING PICTURES OriginalFiled Feb 26, 1924 2 Sheets-Sheet 2 \ZZ A T Z/A f u Q mflmmumjmml 8 Q 25 J 5 000.000.00.00 0 o o o 0 o o o 5 54400441306 RICHARD HOWLAND RANGERor reproducing pictures Patented Mar. 8.1932

" UNITED STATES PATENT OFFICE RICHARD ROWLAND RANGER, OF NEWARK,NEW.J'ERSEY, ASSIGNOR TO RADIO COR- rons'rronor AMERICA,

A CORPORATION OF DELAWARE METHOD OF AN D MEANS FOR REPRODUCING ANDTRANSMITTING PICTURES Original application filed February 26, 1924,Serial No. 695,175. Divided and this application filed February 7, 1929.Serial No. 388,071.

The present invention forms a divisional part of my copendingapplication, Serial No. 695,175, filed February 26, 1924, and relates'to a new and improved process of duplicating or the like and, althoughmy invention may be used for the purpose of producing duplicates andreproductions of pictures or the like at the place where the originalsare found, it is also particularly adapted to produce such duplicates atany distance from the place where said originals are found, utilizingfor the purpose of control. of the reproduction any existing telephone,telegraph or radio circuits.

My invention contemplates as a new article of manufacture a picture orpictorial representation in which the efiects of various intensities oflight are produced in a novel manner, and contemplates also a process bywhich such pictures may be produced. The pictures which I produce andthe process by which I produce them render my invention particularlyuseful for transmitting pictures to a distant point by means oftelephone, telegraph or radio circuits, particularly the latter.

While I have referred to the. use of my invention for producingduplicates of pictures and the like, invention is not limited thereto,but that I may produce duplicates of visual or graphic records of anysort, such for instance, as copies of motion picture films, manuscripts,letters or documents, finger prints and the like, and I therefore wishit understoodthatIhaveused the term picture throughout the specificationand claims in'the broad sense as defined above to include the variousarticles given by way of example and others, as will beunderstood bythose skilled in the art.

It is an object of this invention to produce a picture or a visualrecord in which the ef- 'fects of varying light intensity are producedin a novel manner. o

It is another object of this invention to produce a practical and simpleprocess for duplicating or reproducing pictures.

It is still another object of my invention to produce a process by whichthe reproduction of the picture maybe made at any distance from theoriginal.

it should be undrstood that my -trical Still a further object of myinvention is to v produce a reproduction of an originally transmittedpicture which reproduction closely corresponds to the original and, atthe same time, closely approximates the highly desirable half toneprints.

It is still another object of m invention to produce a process for therepro notion of pictures which is particularly adapted for use intransmitting pictures to'a distance by the use of telephone or telegraphlines or by the use of radio circuits. 4

Still other and ancillary objects of my invention will be apparent fromthe specification.

The novel features which 'I believe to be characteristic of my inventionare set forth with particularity in the appended claims my inventionitself, however, both as to its organization and method of operationwill best be understood by reference to the following description takenin conjunction with the accompanying drawings, in which Fig. 1 shows anarrangement of apparatus adaptedto translate light intensity intoelectrical fluctuations of novel character;

Fig. 2 shows a modified form of apparatus adapted to translate lightintensity into elec fluctuations of novel character, but in the inversesense from those produced by the apparatus of Fig. 1;

Fig. 3 shows an arrangement which is con- Fig. 6 is a typical example ofa picture produced by my process; and

Fig. 7 diagrammatically illustrates a series of lines of a picture ofthe type shown by Fig. 6 as built up from the series of dots illustratedby portion C of Fig. 5.

Broadly speaking, my

invention" contemplates translating the lightintensitms of the pictureto be transmitted'or reproduced progressively into a series of impulsesof substantially uniform duration and intensity, but separated byvariable spacing as shown more particularly by Fig. 5. In this ure, partA represents the intensity of light falling upon the photo cell, part Bthe current impulses produced by relay 21 and part C the recordedimpulses. As will be seen, this figure shows how a positive may beproduced by the recorder from a positive at the transmitter, but as willbe pointed out hereinafter, my invention is adapted equally well toproduce a negative from a positive or vice versa.

While my invention is adapted for reproduction of pictures at a distanceutilizing telephone and telegraph circuits, it is primarily andparticularly adapted for transmission of pictures by radio, andespecially useful in connection with the present high power stationssince the entire transmitting and receiving apparatus may be utilizedwithout change, as the picture to be transmitted is sent out in the formof a series of impulses of uniform intensity and duration. This permitsthe utilization of the full power of the transmitting apparatus on eachimpulse whereby delicate tonal variations in the picture may betransmitted at the full power of the station, thus minimizing the effectof static and other interference on the reception of the picture.Moreover, as the impulses are all of very short time duration, the powerconsumption at the transmitter will be a minimum.

In general, it may be stated that the under lying principles of myinvention consist in utilizing a beam of light, the-intensity of whichis controlled by the picture to be reproduced, and which may be easilyobtained by projecting light upon or through the picture to bereproduced, to control the resistance of a light sensitive element of atype well known in the art. The variations of resistance of the saidelement are then utilized to control the spacing between impulses or thelike of an electrical current or ,wave in such a manner that thespacingperiod is an indication of the intensity of light of the picture.

My invention may take a number of forms. For instance, a direct currentfrom a battery or other local source may be interrupted periodically sayfrom 1 to 10 times per second whereby the spacing time between uniformimpulses is varied in accordance with the light intensity of the pictureto be transmitted or reproduced, or the magnitude of the current may bevaried without total interruption, if desired. In a similar manner andparticularly in using my invention to transmit pictures by radio, analternating-current of any desired frequency may be interrupted orvaried, or again a high frequency oscillating current or so calledcarrier current may be interrupted or varied in amplitude or may havesuperposed thereon currents of lower ing periods, the essentialcharacter of my invention being the translation of a picture intomarking and spacing periods, oneof which is constant and the othervariable.

Referring specifically to Fig. 1, there is provided a transparent drum 1arranged in a manner so that the picture to be reproduced,

may be supported thereon. A suitable source of light herein shown as alamp 2 is arranged in a manner to supply light to said picture, whichlamp in the present instance is shown as mounted within the drum 2, anda suitable lens 3 is provided for condensing the light upon a smallsection ofthe icture. Drum 1 is arranged for rotation an may be drivenby any suitable means, such as a motor, diagrammatically shown and desiated as M. A suitablecabinet 6 is provi ed having a small openingtherein and having a light sensitive cell 5 of any suitable type wellknown in the art mounted within and adapted to have the light fromsource 2 fall thereupon.

The light from source 2 after passing through a section of the pictureis again condensed by lens 4 and'projected upon the light sensitive cell5 within the cabinet 6. While I have indicated that the light 2 isarranged within the drum, it will be readily understood that this is byway of example only and that the light ma be any suitable sourceandarranged in any esired manner, the. only condition to be fulfilled beingthat light from a small section of the picture shall fall upon the lightsensitive cell 5. I

In reproducing the picture, it is of course, necessary that light fromall parts of the pictureto be reproduced should fall upon the lightsensitive cell and a convenient way of providing for this is to arrangedrum 1 upon a support having suitable screw threads, whereby as the drumis rotated by motor M it is also caused to travel slowly in an axialdirection. It will thus be seen that during rotation of the drum, lightfrom each and every part of the picture will be progressivethrough cell5 to the source, and that the point 8 eeaseo value of. this current.will be the greater, the

drop between points 8 and 9 will thus be an indication of the lightintensity of the particularsection ofthe picture from which light isbeing projected upon the cell.

While my invention is not limited to the apparatus shown for utilizingsuch potential dropto create fluctuations, the spacing period of whichis proportional to light intensity, a very satisfactory arrangement isthat shown wherein a three-electrode thermionic relay 10 is connected ina manner to have its input electrodes subjected to the resistance dropproduced across and between points 8 and 9. The cathode of tube 10 isconnected to and the control electrode or grid to The cathode isenergized to produce electron emission by a source of E. M. F. 12 andvariable resistance 11 is provided for maintaining the cathode at theproper temperature to control the degree of electron emission. Connectedin the anode-cathode circuit of said thermionic relay, 1 providecondenser 13 and I provide an additional thermionic relay 14 having itsinput circuit connected across condenser 13 as shown. battery 16, knownin the art as a G or bias battery, is provided for. maintaining thepotential of the grid of tube 14 at the proper value and in the presentinstance I point 9.

have found that satisfactory results are produced when battery 16 has apotential of the order of 60 volts. The cathode of relay 14 isenergizedby any suitable source such, for instance, as source 12, whichalso energizes cathode of relay 10 and an additional variable resistanceis provided for controlling electron emission in relay 14.

Connected in the output circuit of tube 14, I provide winding 17 ofrelay 18 and connected to the opposite terminal of the winding 17 Iprovide a suitable means for maintaining the plate of tube 14 positivesuch, for

as a sou'rce ofE. M. F. 23,-the poinstance,

which may be of the order of 110 tential of volts. The negative'terminalof said source is connected to the common filament circuit of the relays10 and 14 in a manner to complete the plate-filament circuits thereof.In the plate circuit of relaylO, I provide winding 20 of relay 21 and aresistance 19, the function of which will be explained later.

- Also, in series with winding 20 and resistance 19, I provide a relay18 normally maintained in closed position by suitable means, such as aspring as shown, but adaptedto be opened under the action of coil 17under conditions to be explained. The fixed contact of relay 18 isconnected to the anode of tube 10 in a man ner to maintain a potentialdifierence equal to the E. M. F, of'source 23 between the anode andcathode of said tube when relay 18 is closed. Relay 21 controlled bycoil 20 is pro- Icondenser plate current to to open again.

plate voltage is supplied to this tube. Likewise, a negligible spacecurrent will be flowing through relay 14 for the reason that, al-

though plate voltage is applied to this tube, the negative bias impartedto the grid by battery 16 is such as to prevent the flow of spacecurrent in a well known manner.

Now assume that relay 18 is closed due to spring action. Immediatelyplate voltage is applied to relay 10 and condenser 13 begins to chargeand under normal conditions will continue to be charged until itspotential is equal to that'of source 23. It is also to be noted thatimmediately upon the closure of relay 18 this charging current flowingthrough winding 20 causes relay 21 to close. However, as condenser 13begins to charge, the poten- A tial of grid of tube 14 will become morepositive with respect to the filament thereof, and

depending upon the value of batteries 16 and source 23, at some pointduring the charge of condenser 13, grid of tube 14 will reach such apotential that sufficient space current begins to flow in tube 14 andthrough winding 17 to cause relay 18 to be opened, thus cutting theplate voltage off from tube 10 whereupon relay 21 is opened by itsspring. Space current continues to flow in tube 10, being now, however,supplied by the charge remaining upon 13 and as condenser 13 dischargesthrough tube 10, the potential of grid of tube 14 becomes negative,whereupon the space current flowing in tube 14 is reduced, relay 18 isclosed by its spring, and the cycle is repeated.

, It may be pointed out that under normal conditions, relay 18 swings toclosed position followed practically instantly by relay 21, condenser 13is thereupon charged almost immediately and relay 17 is energized, asabove described, causing armature 18 to open, which, by cutting oil thedirect supply of tube 10, also causes relay 21 The cycle of operationswill be continued indefinitely, relay 21 closing for a very shortinterval of time and then opening again, and the time interval betweenopening of relay 2]. and the subsequent closure being dependent, amongother things, on the rate at which condenser 13 discharges, the value ofgrid bias battery 16, and the potential upon the grid of tube 10. Ingeneral, it may be said that the lower the E. M. F. of battery 16 isbelow that of source 23, the

longer such time interval, and it may be noted that by choosing battery16 of Suficiently low value, it is possible to prevent fluctuations ofrelay 21. Under such conditions, for dark spots on the picture, relay 21will close and remain closed as long as the picture is dark. As thepicture becomes light, relay 21 will open and remain open until a darkspot is again reached. Such an adjustment is of value for producingcopies of manuscripts, letters, etc. wherein only two values aredesired. In this connection, it may be noted that by proper adjustmentof bias battery 16 between the low potential giving only two values andthe potential of local source 23, any range of contrasting light valuesmay be obtained in the picture finally produced. However, for a definitevalue of condenser 13 and battery 16, the time interval between theopening of relay 21 and its subsequent closing is strictly dependentupon the intensity of light falling upon the photo sensitive cell 5,since it will be seen that the greater the light intensity the greaterthe negative charge upon the grid of tube 10, and, consequently, theslower condenser 13 will be discharged by the plate of tube 10.

It may be stated that if condenser 13 is allowed to charge very rapidly,the closure and subsequent opening of relay 21 is practicallyinstantaneous and, therefore, I have provided resistance 19 in thecharging circuit of this condenser which allows relay 18, andtherefore-relay 21, to be closed for a length of time sufficient tooperate further relays if desired.

The local circuit controlled by relay 21 and energized by battery 22 maybe used to control, modify, modulate or influence in any desired way aradio or telegraph transmitter in a manner to change the characteristicsof the transmitted effects in accordance with the closures of relay 21,but it should be particularly noted that in the transmission of pie--tures by radio, it is of advantage to use a conventional system whereinthe full power of the station is radiated during the time that relay 21is closed and no power is radiated at other times. Such a result may beaccomplished by a number of ways forming no part of my invention as willbe evident to those skilled in the art. For the purpose of merelyduplicating pictures without transmitting the same, relay 21 may be usedto control a recorder of the type shown in F ig. 4 connected directly incircuit therewith.

Referring to Fig. 2, T have shown an alternative arrangement adapted togive variations in the opposite sense from the apparatus shown inFig. 1. For instance, whereas the apparatus shown in Fig. 1 is adaptedto decrease the spacing intervals for lower intensities of light, thearrangement shown in Fig. 2 is adapted to increase the same, fordecreasing intensity of light. The construction of this arrangement isin general similar eeaeeo to the arrangement shown in Fig. 1, exceptthat the source of supply 23, instead of being cut off from the plate oftube 10 and condenser 13 by theoperation of relay 18, is connectedpermanently thereto through a high resistance 24. Relay 18 is thenconnected as shown in a manner to short circuit condenser 13 whenclosed. The operation is substantially as follows:

Condenser 13 is charged by source 23 through resistance 24 while relay18 is open, and source 23 also supplies plate current for tube 10.Resistance 24 is chosen of such high magnitude that the value of platecurrent flowing in tube 10 has considerable effeet on the time taken tocharge condenser 13. For instance, for a high intensity of light fallingon a photoelectric cell 5, the drop through resistances 8 and 9 will berelatively large and the space current in tube 10 will be small becauseof the negative bias on the grid. Under the circumstances, condenser 13charges quickly. The potential of the grid of tube 14 is thereby quicklycarried over into the range where tube 14 draws plate current. The flowof plate current in tube 14 energizes winding 17 and closes armaturel8.The closure of armature 18 short circuits condenser 13 allowing it todischarge, and the surge of current due to the discharge of condenser 13energizes winding 20 thereby closing relay 21. At the same time, thedischarge of condenser 13 causes the grid of tube 14 to become negativewith respect to the filament in a manner to cut off the flow of platecurrent in the tube, whereupon the operation is repeated.

It will be seen that the flow of plate current in tube 10 has aconsiderable efi'ect on the spacing intervals of relay 21 for the reasonthat when the grid of tube 10 is negative and platecurrent'is cut 011',condenser 13 may charge rapidly. When, however, plate current is flowingin tube 10, which corresponds to a condition of relatively little lighton photo cell 5, part of the current which would otherwise chargecondenser 13, is diverted to supply the plate current for the tube, andtherefore the rate of charge of condenser 13 is slower. I

Referring to Fig. 3, I have shown an arrangement by which it is possibleto obtain in eiiect either the circuit shown in Figs. 1 or 2, dependingon the position of switch arms 24 and 25 which are operated together tocooperate with operating contacts 26-, 27 and 28, and dummy contact 29.It will be seen that when the switch 24, 25 is thrown to the right, thecircuit will be that of Fig. 1; whereas, when thrown to the left will bethat of Fig. 2.

Reception and reproduction of the picture may be accomplished, forinstance, by apparatus such as that shown in Fig. 4, wherein a drum 1 isprovided driven by a motor M I through any suitable arrangement, such asworm and gear. A suitable pen or stylus 35 is mounted in a manner to bebrought into and out of contact with the surface of the drum 1. This maybe accomplished in a number of ways, for instance, as in the arrangementshown wherein the pen 35 is pivoted at a point intermediate its ends andmounted upon a support 36. As shown, a spring 37 normally tends to holdthe point of the said pen out of contact with the surface of drum 1. Anarmature 38 is attached to the pen and c0il.39 is provided forattracting the said armature in such a manner that upon the energizationof coil 39, the pen or stylus is brought into contact with the surfaceof drum 1.

It is obvious that the speed of drums 1 and 1 must be controlled in sucha manner that the angular speed of each is equaland it is also apparentthat the longitudinal travel of drum 1 with repect to pen 35 or viceversa will be controlled in accordance with the travel of drum 1 withrespect to light sensitive cell 5. A practical arrangement forpreventing distortion of the picture due to differences in the travel ofthe two drums is obtained when they are made thesame diameter, driven atthe same speed and caused to travel longitudinally at the same speed.

My invention is not concerned with methods for obtaining the exactsynchronism in speed between the drums 1 and 1, as means are known inthe art for obtaining such synchronism. For instance, two similar motorsmay be used and each regulated by an automatic speed regulator to run atconstant speeds. It is then necessary that coil 39 be subject toimpulses when relay 21 is closed and only at that time. This conditionmay be obtained by operating coil 39 from a radio receiver when theimpulses are transmitted by radio or any other suitable receivingarrangement when they are transmitted in any other way, and obviouslythe impulses may be amplified to any extent desired to obtainsatisfactory operation.

In operation a sheet of paper will be secured to drum 1 and the stylusor pen 35 kept supplied with ink, the motor started and adjusted to thespeed desired. It will then be apparent that the incoming impulses willcause the pen to move against the-drum making dots thereon, as shown inpart 0 of Fig. 5. Upon the completion of the transmission of thepicture, the picture will be found to be reproduced upon the paper ofthe drum and will be similar in appearance to a stippled etching, asshown more particularly by Fig. 6.

Bv Fig. 7 I have illustrated a series of marking pulses to graphicallyrepresent a series of lines of the picture as produced. These linesrepresent marking impulses each of equalduration but variably spaced toportray various tonal values on the picture rec- 0rd. In therepresentation of Fig. 7, no efiort has been made to portray an actualpicture but merely to illustrate the principle involved in producingadjacent linesof the picture in accordance with the teachings of thisinvention.

Obviously other methods of recording may be used. For instance,satisfactory results may be obtained by the use of a photographicrecorder such as has been disclosed in U. S.

Patent No. 1,787,851, granted on January 6,.

1931, upon an'application filed jointly by E. F. W. Alexanderson andmyself for an invention for picture transmission by wire or radio.

While I have shown and described my invention with the particularityrequired to enable those skilled in the art to practice and obtain thebenefits of the same, it will be evident that modifications and changesmay be made without departing from the spir1t and scope of my invention.

Having described my invention, what I claim is: j i

1. A picture consisting solely of a mass of dots of substantiallyuniform intensity disposed upon a background ofdifierent lightintensity, the'relatlve concentration of said dots varyin so as toproduce effects of progressively c anging intensities of light andshadow.

2. A. picture comprising a background of arbitrary light intensityhaving disposed thereon only a mass of uniform points each ofsubstantially equal area and intensity and of differing light intensityfrom said background so as to contrast with said background, the numberof said dots per unit area bemg varied in a manner to produce the effectof light and shadow.

3. A picture comprising a background of varying light value.

RICHARD HOWLAND RANGER.

